Changes in the Spatial Organization of Brain Activity after Combined Antidepressive Therapy Including Transcranial Magnetic Stimulation

Abstract

In order to reveal changes in the spatial organization of brain activity after a course of combined antidepressive therapy, including antidepressants and high-frequency (20 Hz) rhythmic transcranial magnetic stimulation (TMS) of the dorsolateral prefrontal cortex (DLPFC) of the left hemisphere, a multidisciplinary clinical psycho-neurophysiological study was performed on two groups of patients suffering from depression that were receiving a purely medication (control group), or combined (TMS group) therapy. It was shown that after the course of therapy an improvement of the clinical state occured in both groups, although the psychological state and general condition were better in the ТМS group. After the course of therapy, small changes in the spatial organization of brain activity were found in both groups, as reflected in the values of the EEG coherence (Coh), rather than of the spectral power of the EEG. The main changes of Coh in the control group were observed in the α₂ (9–11 Hz), α₃ (11–13 Hz), and θ₁ (4–6 Hz) EEG subbands, while in the ТМS group the changes were seen in the β₂ (20–30 Hz) subband, including the area of direct ТМS action. The results suggest that the therapeutic effect of the combined antidepressive therapy, including high frequency ТМS of the DLPFC of the left hemisphere, was manifested as a more pronounced improvement of psychological and cognitive conditions in the patients of the TMS group, which resulted from activation of not only this cortical area itself as a zone of direct influence of ТМS, but also of other areas of the cortex and subcortical regions that are closely connected with it. The increase of the Coh in lower-frequency EEG bands (α and θ) in other cortical areas may be based on strengthening of inhibitory influences from the prefrontal and orbito-frontal cortices.